The invention relates to dehydrated agricultural products, including dehydrated alfalfa products, and also relates to processes and apparatus for making the dehydrated agricultural products, especially dehydrated alfalfa, and also to apparatus and processes for separating stem and leaf pieces of dehydrated alfalfa.
Conventional methods of harvesting alfalfa put farmers at the mercy of the weather. Alfalfa must be properly dried before it is baled or otherwise processed and stored. Dehydrating devices powered by fossil fields, especially natural gas, long have been utilized to dehydrate alfalfa. Natural gas powered dehydrating systems are commonly used in the United States, but most of the presently operating systems were installed thirty to fifty years ago. In most of these old systems, the air which dehydrates the alfalfa is heated to temperatures of roughly 1600.degree. F. Such high air temperatures rapidly dehydrate gas fuel has risen so high that now there is a great trend in the alfalfa dehydrating industry to allow freshly cut hay to lie on the field as long as possible in order to partially dry it before removing it from the field and passing it through the dehydrator. This is recognized in U.S. Pat. No. 4,193,208 which notes that as fuel costs have increased, it has become common practice to rely more heavily on the benefits of some field curing, notwithstanding the risk of damage or loss resulting from leaving the cut crop in the field during the curing processes, simply because this technique greatly reduces the moisture content of the crop presented to the dehydrator, and consequently lowers the cost of the natural gas required to complete the drying process.
Unfortunately, there are significant disadvantages to using the alfalfa field as a "curing pad" for freshly cut alfalfa. For example, in some parts of the United States, the yearly amount of crop growing time lost as a result of using the field as a curing paid is a large portion of the time required to grow one or more crops. For example, in Yuma, Ariz., as many as ten alfalfa crops per year could be grown and harvested the alfalfa is swathed (i.e., mown and wind rowed) and is immediately "green-chopped" and removed from the field. Using of the field as a "curing pad" for completely or partially sun drying the alfalfa crop for several days for each crop results in a substantial loss of time that could otherwise be used for growing more alfalfa as soon as the previous crop is cut. (Obviously, the field cannot be irrigated while it is being used as a curing pad.)
Furthermore, sun drying, i.e., field curing, of alfalfa causes a great reduction in the nutrient value of alfalfa, sharply reducing the market price which can be obtained for the final product. For example, several of the important nutrients, including chlorophyll, xanthrophylls and Vitamin A deteriorate rapidly as a result of exposure to sunlight and moisture. Sun drying also degrades the color of alfalfa, which greatly reduces its market price. Those skilled in the art know that the color of alfalfa products is very important to buyers because color is known to be a general indicator of the overall quality and nutrient content of alfalfa. Furthermore, alfalfa that is being "field cured" is subject to accumulatihg additional moisture, either in the form of dew or rain. It is well known that when such moisture evaporates due to the sun's rays, a very pronounced bleaching away of the color and nutrients occurs. The exposed stems and leaves both loose substantially all of their green color and a great amount of their nutrient content.
Another shortcoming of completely drying cut alfalfa using the field as a curing paid is that the alfalfa leaves become dry and brittle faster than the stem material and become subject to shattering. For example, a few hours after the alfalfa has been mowed or swathed, the leaves will be dry and brittle enough that an appreciable number of them will break off when the alfalfa is again handled, or even if a strong wind occurs. The subsequent further handling of the brittle crop material, for example, to remove it from the field and finish dehydrating it in a conventional gas fired dehydrating system, causes the brittle leaves to break, and fall to the ground and be lost.
Since the leaf material has a much higher concentration of a number of important nutrients than the stem material, the loss represents a loss of a portion of the most valuable part of the alfalfa crop. Since alfalfa stem material has a substantially higher percentage fiber content than alfalfa leaf material, the loss of leaf material in this fashion results in a higher percentage of stem material content, and hence, fiber content of the total harvested crop, and a lower nutrient content.
Some agricultural experts estimate that the loss of potential weight of alfalfa product produced due to use of an alfalfa field as a curing pad can be as high as 20% to 30% per year.
Another problem that is caused by partially curing alfalfa in the field is caused by the fact that the moisture content of field cured crops may be reduced from approximately 80% down to roughly 50%: this amount of moisture is simply not sufficient to protect the partially dried alfalfa against severe combustion and degradation under the influence of the high air inlet temperatures of all conventional natural gas fired dehydrators.
It has been found that the high temperatures to which most dehydrated alfalfa is actually exposed in known conventional natural gas fired dehydrators causes a significant deterioration in some of the important nutrients of alfalfa, including Vitamin A (carotene), xanthophylls, protein, calcium, phosphorous, arginine, and lysine. Arginine and lysine are essential amino acids. Vitamin A (carotene) is important, contributing to fertility of many animals and poultry.
The importance of avoiding destruction of the nutrient value of alfalfa can perhaps be better appreciated when it is realized that before dehydration, and before exposure to excessive sunlight, alfalfa leaves have very high protein content. It is not as high as soybeans, the meal of which has approximately 44%-49% protein, but nevertheless, alfalfa leaves contain roughly 30% protein. Soybeans are efficiently grown only in certain climates, South America, and the United States being the two largest soybean producing areas of the world. Soybean crops are grown and harvested only once per year. In contrast, alfalfa can be grown in many parts of the world, including both the hotter climates and the colder climates. In the colder climates or at higher elevations, several alfalfa crops per year can be grown and harvested. In irrigated desert areas, for instance, Yuma, Arizona, as many as ten alfalfa crops per year can be grown. In the Southwest U.S., the yield of alfalfa per acre can be approximately ten dried tons per year, whereas the maximum yield for soybean crops is approximately one ton per acre per year. Consequently, the amount of protein available from alfalfa is high, and in the future, it can be reasonably expected that not only animal feed products, but other products for human consumption may rely on alfalfa as a protein source. Even for animal feed purposes, the protein content is one of the most important nutrients in alfalfa, and significantly affects market price. Obviously, it is highly desirable that the reduction of content of protein, as well as the other above-mentioned nutrients, that occurs in conventional alfalfa dehydrating processes be substantially reduced.
U.S. Pat. No. 2,659,161 recognizes the need for using relatively low temperature air to dehydrate alfalfa in order to prevent degradation of carotene therein. However, the apparatus and process disclosed is not satisfactory for use in conjunction with economical alfalfa harvesting apparatus and methods because although the apparatus disclosed does preserve nutrients in alfalfa more effectively than field curing processes and conventional high temperature natural gas fired dehydrating processes, the method and apparatus disclosed in U.S. Pat. No. 2,659,161 has not been popular, probably because that process is not an economic way of attaining the higher nutrient values that would be desirable for alfalfa products purchased by the feed buying public. One reason that the processes disclosed in U.S. Pat. No. 2,659,161 is not economic is that it is necessary to remove alfalfa from the field as soon as possible after it is cut in order to enhance the growing time of the subsequent crop and therefore it is highly desirable to begin dehydrating alfalfa as soon as possible after it is cut. To accomplish this, it is necessary that a particular selection of available conventional farm machinery and a particular work force be able to work efficiently at their normal speed without causing the necessity of temporarily storing large amounts of green cut alfalfa for very long times. This means that the alfalfa dehydrating system must be able to receive the freshly cut and chopped alfalfa product approximately as rapidly as it is supplied by the above-mentioned selection of farm machinery and work force.
German Pat. No. 2836526 discloses a device for drying cereal grains. The system disclosed includes a sloped solar panel from which air flows by convection into a drying tower containing a series of mesh baskets containing the cereal grains. Although the device disclosed use convection to move the solar heated air thorough the system, that system would be totally unsatisfactory for dehydrating alfalfa on a commercial basis.
There is clearly an unmet need for an improved high protein alfalfa product which is not exposed to the high temperatures of most natural gas fired dehydrating systems and does not experience the nutrient loss that results from sun curing of cut alfalfa on the field. Since there are various portions of the alfalfa product which are high in fiber, namely the stem portions, and since there are other portions of alfalfa namely the leaves, which are very high in protein, xanthophylls, and Vitamin A among others, which are highly useful in different types of feeds for different types of animals, it would be highly desirable to be able to efficiently separate the leaves having high nutrient content from the high fiber stems of alfalfa in order to attain high protein, low fiber foods for certain animals, such as pigs, poultry etc. and high fiber feeds for other types of animals such as cattle, horses, etc. having large stomachs or multiple stomachs that are capable of digesting high fiber foods.
Accordingly, it is an object of the invention to provide an improved alfalfa product having high nutrient values, including protein, various vitamins, minerals, amino acids, and low fiber.
It is another object of the invention to economically provide different mixtures of alfalfa stem and leaf material to provide desired ratios of fiber and nutrient values for different food purposes.
It is another object of the invention to substantially reduce the cost of dehydrating alfalfa products.
It is another object of the invention to provide dehydrated alfalfa with uniform product characteristics.
It is another object of the invention to provide dehydrated alfalfa products while incurring much lower energy costs than has been possible in the past.
It is another object of the invention to provide high integrity separation processes and apparatus for dehydrating alfalfa.
It is another object of the invention to provide an economical alfalfa dehydrating system and method that avoids excessive deterioration of nutrients in alfalfa.
It is another object of the invention to provide an economical dehydrating system and method for dehydrating agricultural food products.
It is another object of the invention to provide an economical solar powered alfalfa dehydrating system and method that avoids excessive nutrient deterioration in the alfalfa and operates at a substantially constant rate to receive freshly cut and chopped alfalfa and delivered by a preselected group of farm machinery.
It is another object of the invention to provide a dehydrated alfalfa product with higher nutrient proportions than any prior known dehydrated alfalfa product.
It is another object of the invention to provide a dehydrated alfalfa product having lower fiber content than any known prior dehydrated alfalfa product.
It is another object of the invention to provide an improved solar collector structure suitable for efficiently heating incoming air.
It is another object of the invention to increase the total yield per acre of alfalfa and total production of nutrients per acre of alfalfa.